1. Field of the Invention
The present invention is generally related to a marine propulsion system having a vertical driveshaft extending through the generally horizontal wetted surface of a submerged hull and, more particularly, to an exhaust system that directs exhaust gas from an engine within the bilge, or hull structure, of a marine vessel downwardly through the hull of the marine vessel and to a position that allows the exhaust stream to pass through the hub of a propeller of the marine propulsion device.
2. Description of the Related Art
U.S. Pat. No. 5,108,325, which issued to Livingston et al. on Apr. 28, 1992, discloses a boat propulsion device that mounts through a hole in a bottom surface of a boat. The engine is positioned inside the boat and the propeller drive is positioned under a bottom surface of the boat. The propulsion device includes a mounting assembly, a steering assembly rotatably connecting the drive to the mounting assembly for steering the propeller drive under the boat, a trimming assembly swingingly connecting the drive to the steering assembly for trimming/tilting of the propeller drive under the boat at any steered position, and a driveshaft means providing a drive connection between the engine and the propeller drive at any steered and trimmed position.
U.S. Pat. No. 5,735,718, which issued to Ekwall on Apr. 7, 1998, describes a drive unit for a boat having an engine with a flywheel surrounded by a flywheel casing, a propeller drive housing connected to, but electrically insulated from, the flywheel casing, and an input shaft for the propeller drive housing which is driven and electrically insulated from the flywheel.
U.S. Pat. No. 5,755,605, which issued to Äsberg on May 26, 1998, describes a propeller drive unit. Installation in a boat has two propeller drive units which extend out through individual openings in the bottom of a V-bottomed boat, so that the legs are inclined relative to each other. The leg of one drive unit can be set to turn the boat in one direction at the same time as the leg of the other drive unit can be set to turn the boat in the opposite direction, so that the horizontal counteracting forces acting on the legs cancel each other, while the vertical forces are added to each other to trim the running position of the boat in the water.
U.S. Pat. No. 6,623,320, which issued to Hedlund on Sep. 23, 2003, describes a drive means in a boat. A boat propeller drive with an underwater housing which is connected in a fixed manner to a boat hull and has tractor propellers arranged on that side of the housing facing ahead is described. Arranged in that end portion of the underwater housing facing astern is an exhaust discharge outlet for discharging exhaust gases from an internal combustion engine connected to the propeller drive.
U.S. Pat. No. 6,705,907, which issued to Hedlund on Mar. 16, 2004, describes a drive means in a boat. A boat propeller drive has an underwater housing which is connected in a fixed manner to a boat hull and has tractor propellers arranged on that side of the housing facing ahead. In the rear edge of the underwater housing, a rudder blade is mounted for pivoting about a vertical rudder axis.
U.S. Pat. No. 6,783,410, which issued to Florander et al. on Aug. 31, 2004, describes a drive means in a boat which has an underwater housing which is solidly joined to a boat hull and has pulling propellers on the forward facing side of the housing. At the aft edge of the underwater housing, a rudder is mounted, comprising a first rudder blade mounted in the underwater housing and a second rudder blade mounted on the aft edge of the first rudder blade.
U.S. Pat. No. 6,582,259, which issued to Mansson et al. on Jun. 24, 2003, describes a boat propeller transmission. The transmission has a horizontal input shaft, a bevel gear set, a vertical intermediate shaft, an additional bevel gear set, and at least one horizontal propeller shaft. Between the bevel gear sets, a two speed planetary gear set is engaged, to provide two gear speeds in the same direction between the input shaft and the propeller shaft. A control unit controls the shifting between the low and high gear speed. A sensor senses the position of a gear selector. When the gear selector is in the reverse position, the control unit locks the planetary gear set in the high speed position, regardless of the engine speed.
U.S. Pat. No. 6,439,937, which issued to Mansson et al. on Aug. 27, 2002, describes a boat propeller transmission. Between two bevel gear sets, a two speed planetary gear set is coupled, to provide two gear speeds in the same direction between the input shaft and the propeller shaft. The planetary gear set has a sun gear which can be locked against the housing of the planetary gear set with the aid of a one way clutch.
International Patent Application WO 03/093105, which was filed by Mansson on Apr. 29, 2003, describes a boat hull with an outboard drive. The drive unit comprises an underwater housing mounted on the outside of the hull bottom and a gear housing mounted on the inside of the hull bottom and joined to the underwater housing. Between the underwater housing and the gear housing there is fixed a mounting plate, which, together with a screw down plate, with elastic ring inserts, fixes the drive unit to a flange which is made on the inside of a well surrounding an opening in the hull bottom.
International Patent Application WO 03/093106, which was filed by Arvidsson et al. on Apr. 29, 2003, describes an outboard drive for boats. It comprises an underwater housing, in which two propeller shafts are mounted and are driven via a first bevel gearing enclosed in the underwater housing, and a second bevel gearing enclosed in a gear housing. With the aid of a mounting element joined to the underwater housing in the gear housing, the drive unit can be mounted in an opening in a bottom of a boat hull, with the underwater housing on the outside and the gear housing on the inside of the hull. The mounting element forms a housing which defines, firstly, an oil reservoir for the oil of the drive unit and, secondly, a surrounding chamber through which engine cooling water flows and which is used for cooling the oil in the reservoir.
U.S. Pat. No. 5,403,216, which issued to Salmi et al. on Apr. 4, 1995, describes a ship propulsion arrangement. A main propulsion arrangement for a high power ship or the like comprises an underwater drive unit connected to and turnable by a substantially vertical tubular shaft journaled in the ship. The drive unit and the tubular shaft define a hollow casing enclosing an electrical propulsion motor connected to a propeller shaft which is connected to a driving propeller external to the casing. The casing is, at its inside, supported by several mainly vertical web plates, which are arranged to act, in combination, as elements structurally stiffening and supporting the casing, as elements securing the propulsion motor in place relative to the casing, as elements transmitting to the casing reaction forces to the torque developed by the propulsion motor, and as wall elements of ducts for incoming and outgoing gaseous coolant for the propulsion motor.
U.S. Pat. No. 4,178,873, which issued to Bankstahl on Dec. 18, 1979, discloses an exhaust coupling assembly for a marine sterndrive. The sterndrive includes an inboard engine having an exhaust passageway connected to an outboard drive unit having an exhaust passageway. A transom bracket assembly positioned between the engine and the drive unit permits vertical pivoting of the drive unit for steering and horizontal pivoting of the drive unit for trimming. The improvement includes a first exhaust pipe connected to the inboard engine and a second exhaust pipe connected the drive unit. The first exhaust pipe extends outward through the transom of the boat and has an open end position centered on and adjacent the vertical pivot axis. The second exhaust pipe extends toward and ends in alignment with the end position of the first exhaust pipe to form an interface which includes an opening between the pipe ends.
U.S. Pat. No. 4,526,002, which issued to Bibow on Jul. 2, 1985, discloses an exhaust relief system. The engine of a sterndrive is provided with a vacuum relief valve to relieve any vacuum which may occur in the exhaust manifold, thus preventing water from entering the engine through the exhaust system. The relief valve is connected to allow one-way flow from the intake manifold to the exhaust system, thus providing an essentially closed system.
U.S. Pat. No. 4,601,666, which issued to Wood on Jul. 22, 1986, describes an air exhaust bypass for underwater exhaust systems. The system relates to outboard motors and inboard-outboard motors and more specifically to the underwater exhaust systems built into both of these types of marine propulsion devices. The object of the invention is to provide a method of an apparatus for selectively rerouting the underwater exhaust through a muffled above-water outlet while effectively blocking the underwater exhaust emanations.
U.S. Pat. No. 4,773,215, which issued to Winberg et al. on Sep. 27, 1988, discloses an exhaust control assembly for a marine sterndrive. The propulsion system has an inboard engine with an exhaust, an outboard drive unit operatively coupled to the engine and separated therefrom by a transom having two exhaust passages therethrough, and an exhaust control assembly aft of the engine exhaust and forward of the transom and within the boat. The assembly has an inlet connected to the engine exhaust, and has first and second outlets communicating with the respective exhaust passages extending aft through the transom. A valve in the assembly selectively controls communication of the inlet with the first outlet.
U.S. Pat. No. 4,834,683, which issued to Govan on May 30, 1989, describes an apparatus for reducing exhaust gas pressure in outboard and inboard/outboard motors. The device increases the efficiency of operation of an internal engine used in outboard and inboard/outboard motors. It comprises a generally cylindrical member having inner and outer peripheral shell members defining a cylindrical annular space therebetween, wherein are located a plurality of turbine vanes spanning the annular volume between the inner and outer shell members. Said inner and outer shell members and said plurality of vanes are drivingly connected to the propeller shaft of an outboard motor and are mounted coaxially with the propeller shaft. The device is located in the forward end of the inner propeller hub and rotatably mounted in association with the lower unit of the outboard or inboard/outboard motor so that exhaust gases flowing through the lower unit pass through the annular volume. Upon rotation of the propeller shaft, the plurality of vanes are caused to rotate at the same angular velocity thereof. The vanes are configured in such a way so that the exhaust gases are caused to be moved through the lower unit at an elevated velocity thereby causing a decrease in pressure between the lower unit and the exhaust port of the combustion chambers. Exhaust gases are thereafter expelled from the rear of the propeller unit. The decrease in pressure at the exhaust ports causes the engine operation to be more efficient due to the decrease in work required by the piston or pistons to expel exhaust gases therefrom.
U.S. Pat. No. 4,891,025, which issued to Brandt on Jan. 2, 1990, describes an arrangement in a boat propeller installation. It relates to an arrangement in propeller installations including means for supplying motor exhaust gases to the vicinity of the propeller. The invention is characterized in that a gas outlet is located immediately forwards of the propeller and directs the gas flow towards the sweep of the blade tips of the propeller.
U.S. Pat. No. 4,927,390, which issued to Kudoh et al. on May 22, 1990, describes a gas exhaustion device for an inboard/outboard engine. At least one of the rigid conduits of the exhaust system is provided with a projection to engage and restrain a hose clamp which may be released and inadvertently dropped so as to prevent loss of the hose clamp into an inaccessible area.
U.S. Pat. No. 4,940,434, which issued to Kiesling on Jul. 10, 1990, discloses a marine propulsion unit universal drive assembly with through-bellows exhaust. A pair of generally telescoped bellows surrounds the universal joint and provides an exhaust passage therebetween which communicates between the inboard engine and the sterndrive unit. The inner bellows rotates with the universal joint while the outer bellows is stationary. The bellows are preferably of helical or spiral configuration and the rotating inner bellows forms an exhaust pump. In one embodiment, the bellows are concentrically disposed, while in another embodiment the bellows are eccentrically disposed.
U.S. Pat. No. 5,212,949, which issued to Shiozawa on May 25, 1993, describes an exhaust gas cleaning system for a marine propulsion unit. A plurality of horizontally positioned exhaust ports are located within an engine cylinder head. An exhaust manifold communicates with each of the exhaust ports at a first end and forms a gas collecting pipe at its second end. The second end of the gas collecting pipe is positioned above the exhaust ports.
U.S. Pat. No. 5,352,141, which issued to Shields et al. on Oct. 4, 1994, discloses a marine drive with dual propeller exhaust and lubrication. The drive has a spool positioned at the lower horizontal bore and supporting a dual propeller shaft assembly. An exhaust passage includes a passage in the drive housing communicating with the horizontal bore at the spool and a spool exhaust passage passing exhaust rearwardly through the spool to the propeller through hub exhaust passages, providing through-hub exhaust through dual propellers. An oil passage in the housing communicates with the horizontal bore forwardly of the exhaust passage and lubricates the dual propeller shaft assembly.
U.S. Pat. No. 5,423,701, which issued to Rodskier et al. on Jun. 13, 1995, describes a propeller arrangement for a marine propulsion unit. A double propeller arrangement for a marine propulsion unit, for example of the type which includes a sterndrive, is provided. Each propeller has a hub consisting of an inner sleeve with splines for attachment to a propeller shaft, an outer sleeve with propeller blades, and an elastic bushing between the sleeves. Particular to the propeller arrangement is that the inner sleeve of the respective propeller hubs is provided with an axial passage for the discharge of exhaust gases from an internal combustion engine connected to the propeller drive.
U.S. Pat. No. 5,857,880, which issued to Harada on Jan. 12, 1999, describes a through the hub propulsion unit exhaust system. The system for an outboard motor discharges exhaust gases in front of the propeller for improved acceleration. The discharge of exhaust gases upstream of the propeller produces a cavitation effect about propeller blades when accelerating from low speeds. As a result, the outboard motor accelerates more rapidly. At high speeds, the exhaust gases flow through the propeller hub and discharge behind the propeller. No substantial cavitation effect occurs about the blades, and thus, no significant loss of propulsion efficiency occurs when traveling at high speeds.
U.S. Pat. No. 5,954,554, which issued to Bates on Sep. 21, 1999, describes an outboard drive exhaust system. It increases the reverse thrust produced by the outboard drive. The exhaust system includes a first exhaust passage and a second exhaust passage that stems from the first exhaust passage. A flow control device operates within the exhaust system to control exhaust gas through the second passage depending upon the drive condition of the outboard drive. The flow control device permits exhaust gas flow through the second passage when the outboard drive operates in reverse, while inhibiting exhaust gas flow through the second passage when the outboard drive operates under a forward drive condition. In this manner, the improved exhaust system reduces exhaust gas back pressure and thrust degradation due to exhaust gas entrainment in the propeller when the outboard drive operates in reverse.
U.S. Pat. No. 6,638,124, which issued to Zoubul et al. on Oct. 28, 2003, describes an arrangement in a marine exhaust system. The arrangement includes at least two substantially upstanding exhaust pipe arms that are coupled together in common closed fluid communication with a stern exhaust pipe. A pressure equalizer is fluidly connected between the upstanding exhaust pipe arms. The pressure equalizer is configured to provide sufficient fluid passage from each exhaust pipe arm to another to prevent flow back of sea water to a marine combustion engine associated therewith.
U.S. Pat. No. 5,441,432, which issued to Rodskier et al. on Aug. 15, 1995, describes a boat propeller drive unit. The unit has an anti-cavitation plate above the propeller or propellers and has an exhaust duct extending through the anti-cavitation plate. The exhaust duct has its outer port located on the underside of the anti-cavitation plate level with and just above the sweep of the blade tips of the aft propeller.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
As described above, those skilled in the art of marine propulsion systems are well aware of marine propulsion drives that include a vertical driveshaft which extends through a submerged, generally horizontal, surface of a boat. These types of devices include a housing structure that is suspended below the submerged bottom surface of the marine vessel. The housing is rotatable about a generally vertical axis. Devices of this type which use an internal combustion engine to provide motive power to propellers attached to the housing typically mount the propellers in a tractor arrangement, wherein the propellers pull the housing through the water. In these types of systems, engine exhaust is typically ported through openings in the structure near the rear portion of the housing. This allows the exhaust to flow out of the marine drive structure without affecting the operation of the propellers, as a result of ventilation, because the propellers are located at a position which is forward from the exhaust port. Those skilled in the art of marine propulsion systems are also familiar with various types of outboard motors and sterndrive devices which conduct the flow of exhaust gases through the central portion of the propellers mounted on the marine propulsion device. This allows the exhaust gas to exit from the marine propulsion device, through the hub of the propeller, without adversely affecting the operation of the marine propulsion device.
It would be significantly beneficial if a marine propulsion device which has its driveshaft extending vertically through a generally horizontal submerged bottom surface of a marine vessel could be provided with an exhaust system that allows the exhaust gas to pass through the structure of the marine drive and through the propellers. It would be further beneficial if this type of system could be provided in conjunction with a marine drive that mounts its propeller or propellers behind the housing to provide a thrust in a direction toward the housing. This arrangement would allow a push-type marine propulsion system (as opposed to a tractor-type system) to incorporate the strategy of having a vertical driveshaft extending upwardly through the generally horizontal submerged bottom surface of a boat and also causing the exhaust gas from the internal combustion engine to be efficiently entrained in the swirling water behind the propeller or propellers without causing excessive ventilation of the propeller blades. It should be understood that the term “housing”, as used herein, is intended to refer to the structure which is supported at least partially below the marine vessel and is configured to support the generally vertical drive shaft, generally horizontal propeller shaft, and associated gears and bearings of a marine propulsion system.